core/org.eclipse.stem.ui.ge/src/org/eclipse/stem/ui/ge/servlet/SlideShowServlet.java - stem/org.eclipse.stem - Git at Google

 package org.eclipse.stem.ui.ge.servlet;
 /*******************************************************************************
  * Copyright (c) 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileFilter;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.io.PrintWriter;
 import java.net.URLEncoder;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Date;
 import java.util.Enumeration;
 import java.util.HashMap;

 import javax.servlet.ServletConfig;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.eclipse.stem.ui.Activator;


 /**
  * SlideShowServlet sends back a valid KML file for a GET or POST
  * action
  * <pre>
  * The way that it works is this:
  *
  *    A KML file is launched to GoogleEarth that
  *    has a network link with the following URL
  *    http://localhost:8080/SlideShow/slideshow?id=<id>&amp;folder=<path>
  *    where <id> is a unique id
  *          <path> is the directory containing the
  *            kml files generated by STEM.
  *
  *     GoogleEarth will then issue http GET requests with
  *     the specified URL which will cause this servlet's
  *     doGet() method to be invoked.
  *
  *     It retrieves the correct file in one of 2 ways:
  *
  *     The servlet keeps a map of info keyed by the <id> that
  *     has a list of files that was found in the folder
  *     and a counter that is used to send back the N'th file.
  *     and increment N.
  *
  *     If a filename was specified in the URL
  *       http://localhost:8080/STEM/slideshow?...file=<filename>
  *     then that file will be read and returned to GE.
  *     This file will always be the most recently generated
  *     KML file.  This will help ensure that GE does not fall
  *     behind the STEM simulation.
  * </pre>
  *
  */
 public class SlideShowServlet extends HttpServlet {
     /**
 	 *
 	 */
 	private static final long serialVersionUID = 1L;

 	/**
 	 * Used by this and other servlets to control debug output
 	 */
     public static boolean DEBUG = false;

     //public static boolean DEBUG = true;
     /**
      * change to true to cause output to be sent to console instead
      * of GE
      */
     private static final boolean TEST = false;

     private static final long start = new Date().getTime();
     /**
      * Servlet context.
      *
      */
     public static final String CONTEXT = "STEM";
     /**
      * default folder for KML files.
      */
     static final String STEM_FOLDER = "c:\\tmp\\ge";

     /**
      * collection of information about a session
      * Key = id passed to servlet
      *
      */

     private static HashMap<String,SlideShowInfo> _infoMap = null;

     /**
      * set true when we get a request that only sets the BBox info
      */
     private boolean bboxSet = false;
     /**
      *  Handle the initial setup
      */
 	public void init(ServletConfig config) throws ServletException {
 		    super.init(config);
 		    //debug("init: Default folder="+STEM_FOLDER);

 		    _infoMap = new HashMap<String,SlideShowInfo>();

 	 }

 	/* (non-Javadoc)
 	 * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
 	 */
 	protected void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

 		doPost(request, response);
 }

     /* (non-Javadoc)
      * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
      */
     protected void doPost(HttpServletRequest request,HttpServletResponse response)
             throws ServletException, IOException {

 		int counter = 0;

 	    String fileName = null;
 		SlideShowInfo info = null;

 		File[] files = null;

 		try {
 			// get info from url
 			info = getParameters(request);
 			String key = info.getKey();
 			if (bboxSet) {
 				// This was a request to return BBOX only
 				processNoOp(request,response);
 			}
 			// make sure there is some delay between requests
 			info.delay();
 			fileName = info.getFileName();
 			if (fileName != null) {
 				// get a specific file

 				processFile(request,response,info,fileName);
 				return;
 			} else {
 			  // get saved list of files
 			  files = info.getFiles();
 			  // if never filled in
 			  if (files == null) {
 				  // get updated list of files
 				 files = getFiles(info);
 			  }

 			}
 			counter = getCounter(request,response,info);
 			// getCounter will have updated info.getFiles
 			files = info.getFiles(); // added files
 			if (files.length == 0) {
 				// if no .kml files in folder
 				if (info.isWaitForKML()) {
 					sendScreenOverlay(request, response, "Waiting to Start");

 				} else {
 					response.sendError(HttpServletResponse.SC_BAD_REQUEST,
 					"No KML files in specified folder.");
 				}
 				return;
 			}
 			File kmlFile = files[counter];
 //			String print = "key: "+key+" Counter: " + counter +
 //			" addr: " + request.getServerName() + ":"+request.getServerPort()+
 //			" #files: "+files.length +
 //			" kmlFile: "+kmlFile.getAbsolutePath();
 			//debug(print);
 			debug("Send to GE: "+kmlFile);

 			FileInputStream fis = new FileInputStream(kmlFile);
 			// insert is additioal KML to be sent with output
 			String[] insert = info.getInsert();

 			sendOutput(request,response, fis,insert );
 			info.setCounter(counter);
 			_infoMap.put(key, info);
 		} catch (Throwable e) {
 			e.printStackTrace();
 			response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
 					e.getMessage());
 		}
 	}


     /**
      * Get the counter that keeps track of which file
      * is to be processed next.
      *
      * It does more thatn just get the next value for the counter,
      * it will check if there are more files to process and if not
      * do the handling of this case.
      *
      * @param request  ServletRequest
      * @param response ServletResponse
      * @param info   instance of information saved from step to step
      * @return N where we want to display the Nth file
      *           from the specified folder.
      *           0 if starting over
      *
      * @throws Exception
      */
     synchronized
     private int getCounter(HttpServletRequest request,
     		               HttpServletResponse response,
     		               SlideShowInfo info)
                                throws Exception{

 		int counter = info.getCounter();
 		counter++;

 		// if done all of files currently in list
 		int waits = 10; // wait for 10 seconds
 		int max = info.getFiles().length;
 		while (true) {

 		  if (counter >= max) {
  			 // reached end of filelist

 			if (info.isWaitForKML()) {
 				Thread.sleep(1*1000);
 			    info.setFiles(null);
 			    getFiles(info);
 			    max = info.getFiles().length;

 			    waits--;
 			    if (waits > 0)
 			    	continue;
 			    // waited and still no more files
 			    // indicate to user we are paused
 			    counter = max-1;
 			    if (! info.isPause()) {
 					// if we have not yet claimed to be pausing
 			        //debug("pause: ");
                     info.setPause(true);
 			        // send pause as icon to GE
                     String host = getHost(request);
     		    	String url = "http://"+host+"/"+
     				    CONTEXT+"/image?text="+
     				    URLEncoder.encode("Paused","UTF-8");
     				String[] insert = buildScreenOverlay(url);
     				info.setInsert(insert);
 			    }
 			    break;
 			} else {
 				// pause before restarting
 				// TODO remove debug
 				debug("Pause 10 seconds before restarting");
 				Thread.sleep(10*1000);
 				counter = 0;
 				break;
 			}
 		  } else {
 			if (info.isPause()) {
 				//debug("Change pause to active");
 				// we were paused so change image to active
 				info.setPause(false);
 				Thread.sleep(2*1000);
 				String host = getHost(request);
 		    	String url = "http://"+host+"/"+
 				    CONTEXT+"/image?text="+
 				    URLEncoder.encode("Active","UTF-8");

 				String[] insert = buildScreenOverlay(url);
 				info.setInsert(insert);

 			}
 			break;
 		  }
 		} // while(true)

 		return counter;

     }
     /**
      * send back an empty response
      *
      * @param request
      * @param response
      *
      * @throws ServletException
      * @throws IOException
      */

 	private void processNoOp(HttpServletRequest request,
 			HttpServletResponse response)
 	               throws ServletException, IOException{
 		try {

 			PrintWriter os = new PrintWriter(response.getOutputStream());
 			//PrintStream os = System.out;
 			response.setContentType("application/keyhole");

 			os.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
 			os.println("<kml xmlns=\"http://earth.google.com/kml/2.0\">");
 			os.println("<Document>");
 			os.println("</Document>");
 			os.println("</kml>");

 			os.flush();
 		} catch (Throwable e) {
 			e.printStackTrace();
 			response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,e.getMessage());
 		}
 	}
     /**
      * Process a request to serve up a specific file
      *
      * @param request
      * @param response
      * @param fileName
      * @throws ServletException
      * @throws IOException
      */

 	private void processFile(HttpServletRequest request,
 			HttpServletResponse response,
 			SlideShowInfo info, String fileName)
 	               throws ServletException, IOException{
 		try {

 			File kmlFile = new File(fileName);
 			String oldFileName = fileName.replace("_Current","_Old");
 			File oldFile = new File(oldFileName);
 			String[] insert = info.getInsert();
 			FileInputStream fis  = null;
 			int counter = 0;
             while (true) {
 			    try {
 			    	if (! kmlFile.exists() ) {
 			    		Thread.sleep(2*1000);
 			    		counter++;
 			    		// after 20 seconds use old file
 			    		if (counter > 10) {
 			    			rename(oldFile,kmlFile);
 			    		}
 			    		continue;
 			    	}
 					fis = new FileInputStream(kmlFile);
 					//debug(" kmlFile: "+kmlFile.getAbsolutePath());
 					break;
 				} catch (Exception e) {
 					error("processFile failed",e);
 					return;
 				}
             }
             debug("Send to GE: "+kmlFile);
             sendOutput(request,response, fis,insert );

             rename(kmlFile,oldFile);

 		} catch (Throwable e) {
 			e.printStackTrace();
 			response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,e.getMessage());
 		}
 	}


 	/**
 	 * switch files by renaming
 	 */
 	private boolean rename(File oldFile, File newFile) {
 		try {
 			if (newFile.exists())
 				newFile.delete();

 			oldFile.renameTo(newFile);
 		} catch (RuntimeException e) {
 			return false;
 		}
 		return true;
 	}
 	/**
 	 * @param request
 	 */
 	private String getHost(HttpServletRequest request) {
 		int port = request.getServerPort();
 		String host = request.getServerName()+":"+port;
 		return host;
 	}

     /**
      * Get the list of files in the folder
      *
      *
      * @param info  instance that holds misc info about session
      * @return array of Files in the specified folder
      */

     public File[] getFiles(SlideShowInfo info) {
 		File[] files = null;
 		File folder = null;
 		try {
 			files = info.getFiles();

 			if (files == null || files.length == 0) {
 				folder = new File(info.getFolderName());
 			    files = fileList(folder);
 			    if (files == null)
 					files = new File[0];
 			    info.setFiles(files);
 			}
 		} catch (RuntimeException e) {

 			error("getFiles() failed. ",e);
 			files = new File[0];
 		}

 		return files;
     }

 /**
  * get the list of files in the specified folder.
  * The files will only be files with the ".kml"
  * extension and will be sorted by filename.
  * Also netlink files will be filtered out
  *
  * @param folder Directory that contains KML files to display
  * @return array of sorted filenames
  */

   private File[] fileList(File folder) {

     FileFilter ff = new FileFilter() {
 		public boolean accept(File f){
 			if (f.getName().toLowerCase().startsWith("net")) {
 				return false;
 			}
 			if (f.getName().toLowerCase().endsWith(".kml")) {
 				return true;
 			}
 			return false;
 		}
 	};

 	Comparator<? super File> compare = new Comparator<File>() {
 		public int compare(File o1, File o2) {
 			File f1 = (File)o1;
 			File f2 = (File)o2;
 			int answer = f1.getName().compareTo(f2.getName());
 			return answer;
 		}

 	};

 	try {
 		File[] files = folder.listFiles(ff);
 		if (files == null) {
 			return new File[0];
 		}
 		Arrays.sort(files,0,files.length,compare);
 		return files;
 	} catch (Exception e) {
 		e.printStackTrace();
 		return null;
 	}
   }
   /**
 	 * Obtain the following parameters from the URL.
 	 * <pre>
 	 *  id:  A key that makes this session unique
 	 *    Because GoogleEarth sets up a new session for each
      *   request, we cannot use the normal Servlet session
      *   protocol.
      *   We keep a hashmap of session info keyed by an ID that
      *   is passed in the URL
      *
      *  folder:  Where to find the KML files
      *
      *  delay:   Time to delay between returning data
      *
      *  wait:    If "y" them if now new files send a "pause" icon
      *
      *  file:    If spcified then return the specified file
      *
 	 *  BBOX:    If found then GE has return the current view coordinates
 	 *
 	 *  BBoxSet: If found then GE has returned BBOX and no answer is
 	 *           required.
 	 *
 	 *  id is then used to access infoMap and
 	 *  and return an instance of SlideShowInfo which contains current
 	 *  cycle counter, array of files and boolean wait indicator.
 	 *  If there is no existing entry then it builds a new
 	 *  SlideShowInfo instance from the url parameters and stores
 	 *  it in the infoMap.
 	 *
 	 * @param request  Servlet request instance.
 	 * @return instance of SlideShowInfo
 	 */
 	private SlideShowInfo getParameters(HttpServletRequest request) {
 		// get the id from the URL parameters.
 		// http://localhost:8080/slideshow?id=useridkey
 		String mykey="DEFAULT";
 	    String folderName = STEM_FOLDER;
 	    boolean waitForKML = false;
 	    String fileName = null;
 	    String delay = "2";
 	    String bbox = null;
 	    bboxSet = false;
 		Enumeration e = request.getParameterNames();
 		StringBuffer sb = new StringBuffer();
 		while (e.hasMoreElements()) {
 			String name = (String)e.nextElement();
 			String value = (String)request.getParameter(name);
 			sb.append(name+": "+value+" ");
 			if (name.equals("id")) {
 				mykey = value;
 			} else if (name.equals("folder")) {
 				folderName = value;
 			} else if (name.equals("delay")) {
 				delay = value;

 			} else if (name.equals("wait")) {
 				if (value.equals("y")) {
 					waitForKML = true;
 				}
 			} else if (name.equals("file")) {
 				fileName = value;
 			} else if (name.equals("BBOX")) {
 				bbox = value;
 			} else if (name.equals("bboxSet")) {
 				bboxSet = true;
 			}
 		}
 		//debug("getParameters: "+sb.toString());
 		SlideShowInfo info = _infoMap.get(mykey);
 		if (info == null) {
 			info = new SlideShowInfo(mykey,folderName,waitForKML,
 					                 fileName,delay);
 		}
 		if (bbox != null)
 			info.setBBOX(bbox);
 		_infoMap.put(mykey,info);
 		return info;

 	}
 	/**
 	 * Send the KML file to the caller (GoogleEarth)
 	 *
 	 * If TEST=true then it will be written to the browser
 	 * for testing.
 	 *
      * @param request
      * @param response
      * @param kml  InputStream holding file contents
      * @param insert  KML to be inserted in output
      * @throws IOException
      */
     synchronized
     private void sendOutput(HttpServletRequest request,
 			                HttpServletResponse response,
 			                InputStream  kml, String[] insert)
 	            throws IOException {
     	// set TEST=true to get readable output instead of
     	// launching a KML file

 		response.setContentType("application/keyhole");


 		try {
 			OutputStream os = response.getOutputStream();
 			if (TEST) {
 				os = System.out;
 			}
 			copy(kml,os,insert);
 		} catch (Exception e) {
 			String msg = "SlideShowServlet.sendOutput() failed while sending kmlFile";
 			error(msg+"\n"+e.getMessage(),null);

 		}

 	}
     /**
      * build a segment of KML to be inserted into the
      * output written to GoogleEarth.
      *
      * @param url
      * @return KML to be inserted
      */
     private String[] buildScreenOverlay( String url) {
 		String[] insert = new String[]
 			{"<ScreenOverlay id=\"Status\">",
 			 "   <description>STEM status</description>",
 			 "   <name>Status</name>\n",
 			 "<icon>",
 			 "<href>",
 			 url,
 			 "</href>",
 			 "</icon>\n",
 			 // following positions image to loop left
 			 "<overlayXY x=\"0\" y=\"1\" xunits=\"fraction\" yunits=\"fraction\"/>\n",
 			 "<screenXY x=\"0\" y=\"1\" xunits=\"fraction\" yunits=\"fraction\"/>\n",
 			 // use actual size of image
 			 "<size x=\"0\" y=\"0\" xunits=\"fraction\" yunits=\"fraction\"/>\n",
 			 "</ScreenOverlay>\n"
 			 };

 		return insert;
 	}
 	/**
 	 * Send the KML file to the caller (GoogleEarth)
 	 *
 	 *
 	 * @param response
 	 * @param info
 	 * @param msg A string that will be converted
 	 *      to an image and displayed by GoogleEarth
 	 * @throws IOException
 	 */

     private void sendScreenOverlay(HttpServletRequest request,
 			                HttpServletResponse response,
 			                String msg)
 	            throws IOException {

 		response.setContentType("application/keyhole");


 		try {
 			String host = getHost(request);
 			String url = "http://"+host+"/"+
 			     CONTEXT+"/image?text="+
 			URLEncoder.encode(msg,"UTF-8");

 			String[] insert = buildScreenOverlay(url);

 			PrintWriter os = new PrintWriter(response.getOutputStream());
 			//PrintStream os = System.out;
 			response.setContentType("application/keyhole");

 			os.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
 			os.println("<kml xmlns=\"http://earth.google.com/kml/2.0\">");
 			os.println("<Document>");
 			for (int i=0; i<insert.length; i++) {
 				os.println(insert[i]);
 			}
 			os.println("</Document>");
 			os.println("</kml>");

 			os.flush();
 		} catch (Exception e) {
 			String emsg = "SlideShowServlet.sendScreenOverlay() failed while writing kmlFile";
 			error(emsg+"\n"+e.getMessage(),null);

 		}

 	}


 	private static String getClock() {
 		long now = new Date().getTime()-start;
 		return Long.toString(now);
 	}

 	/**
 	 * return the info instance associated with the specified key
 	 * @param key
 	 * @return instance of SlideShowInfo
 	 */
 	public static SlideShowInfo getInfo(String key) {
 		SlideShowInfo info = _infoMap.get(key);
 		return info;
 	}
 	/**
 	 * copy a KML file to the servlet response output stream
 	 * and perhaps insert additional KML statements
 	 *
 	 * @param is KML file input
 	 * @param os Servlet response output stream
 	 * @param insert optional statements to be inserted
 	 *               after the <document> statement.
 	 */
 	private void copy(InputStream is, OutputStream os, String[] insert)
 	       throws IOException {

 		InputStreamReader isr = new InputStreamReader(is);
         BufferedReader br = new BufferedReader(isr);
 		String line = null;


 		try {

 			while (true) {
 				line = br.readLine();
 				if (line == null)
 					break;

 				byte[] buffer = line.getBytes();
 				os.write(buffer, 0, buffer.length);
 				if (insert!=null &&
 						line.toLowerCase().startsWith("<document>")) {
 					for (int i=0; i<insert.length; i++) {
 						buffer = insert[i].getBytes();
 						os.write(buffer, 0, buffer.length);
 					}
 				}
 			}
 			os.flush();
 			os.close();
 			is.close();
 		} catch (Throwable e) {

 			error("SlideShowServlet.copy(): Error while copying KML file. "
 					+e.toString(),null);
 			try {
 				is.close();
 				os.close();
 			} catch (Exception e2) {
 				// already reported it
 			}
 		}

     }

 	  /**
      * print debug messages to the server log.
      * @param msg
      */
 	public static void debug(String msg) {
 		if (DEBUG) {
 		  Activator.logInformation(getClock()+" GEServlet: "+msg);
 		}
 	}

 	/**
 	 * debug output for exceptions
 	 * @param msg
 	 * @param e
 	 */
 	public static void error(String msg,Throwable e) {
 		//log(msg,e);
 		Activator.logInformation(msg);
 		if (e != null)
 			if (DEBUG)
 				e.printStackTrace();
 			else
 				Activator.logInformation(e.toString());

 	}
 }  // class
	package org.eclipse.stem.ui.ge.servlet;
	/*******************************************************************************
	* Copyright (c) 2006 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	import java.io.BufferedReader;
	import java.io.File;
	import java.io.FileFilter;
	import java.io.FileInputStream;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.InputStreamReader;
	import java.io.OutputStream;
	import java.io.PrintWriter;
	import java.net.URLEncoder;
	import java.util.Arrays;
	import java.util.Comparator;
	import java.util.Date;
	import java.util.Enumeration;
	import java.util.HashMap;

	import javax.servlet.ServletConfig;
	import javax.servlet.ServletException;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;

	import org.eclipse.stem.ui.Activator;


	/**
	* SlideShowServlet sends back a valid KML file for a GET or POST
	* action
	* <pre>
	* The way that it works is this:
	*
	* A KML file is launched to GoogleEarth that
	* has a network link with the following URL
	* http://localhost:8080/SlideShow/slideshow?id=<id>&folder=<path>
	* where <id> is a unique id
	* <path> is the directory containing the
	* kml files generated by STEM.
	*
	* GoogleEarth will then issue http GET requests with
	* the specified URL which will cause this servlet's
	* doGet() method to be invoked.
	*
	* It retrieves the correct file in one of 2 ways:
	*
	* The servlet keeps a map of info keyed by the <id> that
	* has a list of files that was found in the folder
	* and a counter that is used to send back the N'th file.
	* and increment N.
	*
	* If a filename was specified in the URL
	* http://localhost:8080/STEM/slideshow?...file=<filename>
	* then that file will be read and returned to GE.
	* This file will always be the most recently generated
	* KML file. This will help ensure that GE does not fall
	* behind the STEM simulation.
	* </pre>
	*
	*/
	public class SlideShowServlet extends HttpServlet {
	/**
	*
	*/
	private static final long serialVersionUID = 1L;

	/**
	* Used by this and other servlets to control debug output
	*/
	public static boolean DEBUG = false;

	//public static boolean DEBUG = true;
	/**
	* change to true to cause output to be sent to console instead
	* of GE
	*/
	private static final boolean TEST = false;

	private static final long start = new Date().getTime();
	/**
	* Servlet context.
	*
	*/
	public static final String CONTEXT = "STEM";
	/**
	* default folder for KML files.
	*/
	static final String STEM_FOLDER = "c:\\tmp\\ge";

	/**
	* collection of information about a session
	* Key = id passed to servlet
	*
	*/

	private static HashMap<String,SlideShowInfo> _infoMap = null;

	/**
	* set true when we get a request that only sets the BBox info
	*/
	private boolean bboxSet = false;
	/**
	* Handle the initial setup
	*/
	public void init(ServletConfig config) throws ServletException {
	super.init(config);
	//debug("init: Default folder="+STEM_FOLDER);

	_infoMap = new HashMap<String,SlideShowInfo>();

	}

	/* (non-Javadoc)
	* @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	*/
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {

	doPost(request, response);
	}

	/* (non-Javadoc)
	* @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	*/
	protected void doPost(HttpServletRequest request,HttpServletResponse response)
	throws ServletException, IOException {

	int counter = 0;

	String fileName = null;
	SlideShowInfo info = null;

	File[] files = null;

	try {
	// get info from url
	info = getParameters(request);
	String key = info.getKey();
	if (bboxSet) {
	// This was a request to return BBOX only
	processNoOp(request,response);
	}
	// make sure there is some delay between requests
	info.delay();
	fileName = info.getFileName();
	if (fileName != null) {
	// get a specific file

	processFile(request,response,info,fileName);
	return;
	} else {
	// get saved list of files
	files = info.getFiles();
	// if never filled in
	if (files == null) {
	// get updated list of files
	files = getFiles(info);
	}

	}
	counter = getCounter(request,response,info);
	// getCounter will have updated info.getFiles
	files = info.getFiles(); // added files
	if (files.length == 0) {
	// if no .kml files in folder
	if (info.isWaitForKML()) {
	sendScreenOverlay(request, response, "Waiting to Start");

	} else {
	response.sendError(HttpServletResponse.SC_BAD_REQUEST,
	"No KML files in specified folder.");
	}
	return;
	}
	File kmlFile = files[counter];
	// String print = "key: "+key+" Counter: " + counter +
	// " addr: " + request.getServerName() + ":"+request.getServerPort()+
	// " #files: "+files.length +
	// " kmlFile: "+kmlFile.getAbsolutePath();
	//debug(print);
	debug("Send to GE: "+kmlFile);

	FileInputStream fis = new FileInputStream(kmlFile);
	// insert is additioal KML to be sent with output
	String[] insert = info.getInsert();

	sendOutput(request,response, fis,insert );
	info.setCounter(counter);
	_infoMap.put(key, info);
	} catch (Throwable e) {
	e.printStackTrace();
	response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
	e.getMessage());
	}
	}


	/**
	* Get the counter that keeps track of which file
	* is to be processed next.
	*
	* It does more thatn just get the next value for the counter,
	* it will check if there are more files to process and if not
	* do the handling of this case.
	*
	* @param request ServletRequest
	* @param response ServletResponse
	* @param info instance of information saved from step to step
	* @return N where we want to display the Nth file
	* from the specified folder.
	* 0 if starting over
	*
	* @throws Exception
	*/
	synchronized
	private int getCounter(HttpServletRequest request,
	HttpServletResponse response,
	SlideShowInfo info)
	throws Exception{

	int counter = info.getCounter();
	counter++;

	// if done all of files currently in list
	int waits = 10; // wait for 10 seconds
	int max = info.getFiles().length;
	while (true) {

	if (counter >= max) {
	// reached end of filelist

	if (info.isWaitForKML()) {
	Thread.sleep(1*1000);
	info.setFiles(null);
	getFiles(info);
	max = info.getFiles().length;

	waits--;
	if (waits > 0)
	continue;
	// waited and still no more files
	// indicate to user we are paused
	counter = max-1;
	if (! info.isPause()) {
	// if we have not yet claimed to be pausing
	//debug("pause: ");
	info.setPause(true);
	// send pause as icon to GE
	String host = getHost(request);
	String url = "http://"+host+"/"+
	CONTEXT+"/image?text="+
	URLEncoder.encode("Paused","UTF-8");
	String[] insert = buildScreenOverlay(url);
	info.setInsert(insert);
	}
	break;
	} else {
	// pause before restarting
	// TODO remove debug
	debug("Pause 10 seconds before restarting");
	Thread.sleep(10*1000);
	counter = 0;
	break;
	}
	} else {
	if (info.isPause()) {
	//debug("Change pause to active");
	// we were paused so change image to active
	info.setPause(false);
	Thread.sleep(2*1000);
	String host = getHost(request);
	String url = "http://"+host+"/"+
	CONTEXT+"/image?text="+
	URLEncoder.encode("Active","UTF-8");

	String[] insert = buildScreenOverlay(url);
	info.setInsert(insert);

	}
	break;
	}
	} // while(true)

	return counter;

	}
	/**
	* send back an empty response
	*
	* @param request
	* @param response
	*
	* @throws ServletException
	* @throws IOException
	*/

	private void processNoOp(HttpServletRequest request,
	HttpServletResponse response)
	throws ServletException, IOException{
	try {

	PrintWriter os = new PrintWriter(response.getOutputStream());
	//PrintStream os = System.out;
	response.setContentType("application/keyhole");

	os.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
	os.println("<kml xmlns=\"http://earth.google.com/kml/2.0\">");
	os.println("<Document>");
	os.println("</Document>");
	os.println("</kml>");

	os.flush();
	} catch (Throwable e) {
	e.printStackTrace();
	response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,e.getMessage());
	}
	}
	/**
	* Process a request to serve up a specific file
	*
	* @param request
	* @param response
	* @param fileName
	* @throws ServletException
	* @throws IOException
	*/

	private void processFile(HttpServletRequest request,
	HttpServletResponse response,
	SlideShowInfo info, String fileName)
	throws ServletException, IOException{
	try {

	File kmlFile = new File(fileName);
	String oldFileName = fileName.replace("_Current","_Old");
	File oldFile = new File(oldFileName);
	String[] insert = info.getInsert();
	FileInputStream fis = null;
	int counter = 0;
	while (true) {
	try {
	if (! kmlFile.exists() ) {
	Thread.sleep(2*1000);
	counter++;
	// after 20 seconds use old file
	if (counter > 10) {
	rename(oldFile,kmlFile);
	}
	continue;
	}
	fis = new FileInputStream(kmlFile);
	//debug(" kmlFile: "+kmlFile.getAbsolutePath());
	break;
	} catch (Exception e) {
	error("processFile failed",e);
	return;
	}
	}
	debug("Send to GE: "+kmlFile);
	sendOutput(request,response, fis,insert );

	rename(kmlFile,oldFile);

	} catch (Throwable e) {
	e.printStackTrace();
	response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,e.getMessage());
	}
	}


	/**
	* switch files by renaming
	*/
	private boolean rename(File oldFile, File newFile) {
	try {
	if (newFile.exists())
	newFile.delete();

	oldFile.renameTo(newFile);
	} catch (RuntimeException e) {
	return false;
	}
	return true;
	}
	/**
	* @param request
	*/
	private String getHost(HttpServletRequest request) {
	int port = request.getServerPort();
	String host = request.getServerName()+":"+port;
	return host;
	}

	/**
	* Get the list of files in the folder
	*
	*
	* @param info instance that holds misc info about session
	* @return array of Files in the specified folder
	*/

	public File[] getFiles(SlideShowInfo info) {
	File[] files = null;
	File folder = null;
	try {
	files = info.getFiles();

	if (files == null \|\| files.length == 0) {
	folder = new File(info.getFolderName());
	files = fileList(folder);
	if (files == null)
	files = new File[0];
	info.setFiles(files);
	}
	} catch (RuntimeException e) {

	error("getFiles() failed. ",e);
	files = new File[0];
	}

	return files;
	}

	/**
	* get the list of files in the specified folder.
	* The files will only be files with the ".kml"
	* extension and will be sorted by filename.
	* Also netlink files will be filtered out
	*
	* @param folder Directory that contains KML files to display
	* @return array of sorted filenames
	*/

	private File[] fileList(File folder) {

	FileFilter ff = new FileFilter() {
	public boolean accept(File f){
	if (f.getName().toLowerCase().startsWith("net")) {
	return false;
	}
	if (f.getName().toLowerCase().endsWith(".kml")) {
	return true;
	}
	return false;
	}
	};

	Comparator<? super File> compare = new Comparator<File>() {
	public int compare(File o1, File o2) {
	File f1 = (File)o1;
	File f2 = (File)o2;
	int answer = f1.getName().compareTo(f2.getName());
	return answer;
	}

	};

	try {
	File[] files = folder.listFiles(ff);
	if (files == null) {
	return new File[0];
	}
	Arrays.sort(files,0,files.length,compare);
	return files;
	} catch (Exception e) {
	e.printStackTrace();
	return null;
	}
	}
	/**
	* Obtain the following parameters from the URL.
	* <pre>
	* id: A key that makes this session unique
	* Because GoogleEarth sets up a new session for each
	* request, we cannot use the normal Servlet session
	* protocol.
	* We keep a hashmap of session info keyed by an ID that
	* is passed in the URL
	*
	* folder: Where to find the KML files
	*
	* delay: Time to delay between returning data
	*
	* wait: If "y" them if now new files send a "pause" icon
	*
	* file: If spcified then return the specified file
	*
	* BBOX: If found then GE has return the current view coordinates
	*
	* BBoxSet: If found then GE has returned BBOX and no answer is
	* required.
	*
	* id is then used to access infoMap and
	* and return an instance of SlideShowInfo which contains current
	* cycle counter, array of files and boolean wait indicator.
	* If there is no existing entry then it builds a new
	* SlideShowInfo instance from the url parameters and stores
	* it in the infoMap.
	*
	* @param request Servlet request instance.
	* @return instance of SlideShowInfo
	*/
	private SlideShowInfo getParameters(HttpServletRequest request) {
	// get the id from the URL parameters.
	// http://localhost:8080/slideshow?id=useridkey
	String mykey="DEFAULT";
	String folderName = STEM_FOLDER;
	boolean waitForKML = false;
	String fileName = null;
	String delay = "2";
	String bbox = null;
	bboxSet = false;
	Enumeration e = request.getParameterNames();
	StringBuffer sb = new StringBuffer();
	while (e.hasMoreElements()) {
	String name = (String)e.nextElement();
	String value = (String)request.getParameter(name);
	sb.append(name+": "+value+" ");
	if (name.equals("id")) {
	mykey = value;
	} else if (name.equals("folder")) {
	folderName = value;
	} else if (name.equals("delay")) {
	delay = value;

	} else if (name.equals("wait")) {
	if (value.equals("y")) {
	waitForKML = true;
	}
	} else if (name.equals("file")) {
	fileName = value;
	} else if (name.equals("BBOX")) {
	bbox = value;
	} else if (name.equals("bboxSet")) {
	bboxSet = true;
	}
	}
	//debug("getParameters: "+sb.toString());
	SlideShowInfo info = _infoMap.get(mykey);
	if (info == null) {
	info = new SlideShowInfo(mykey,folderName,waitForKML,
	fileName,delay);
	}
	if (bbox != null)
	info.setBBOX(bbox);
	_infoMap.put(mykey,info);
	return info;

	}
	/**
	* Send the KML file to the caller (GoogleEarth)
	*
	* If TEST=true then it will be written to the browser
	* for testing.
	*
	* @param request
	* @param response
	* @param kml InputStream holding file contents
	* @param insert KML to be inserted in output
	* @throws IOException
	*/
	synchronized
	private void sendOutput(HttpServletRequest request,
	HttpServletResponse response,
	InputStream kml, String[] insert)
	throws IOException {
	// set TEST=true to get readable output instead of
	// launching a KML file

	response.setContentType("application/keyhole");


	try {
	OutputStream os = response.getOutputStream();
	if (TEST) {
	os = System.out;
	}
	copy(kml,os,insert);
	} catch (Exception e) {
	String msg = "SlideShowServlet.sendOutput() failed while sending kmlFile";
	error(msg+"\n"+e.getMessage(),null);

	}

	}
	/**
	* build a segment of KML to be inserted into the
	* output written to GoogleEarth.
	*
	* @param url
	* @return KML to be inserted
	*/
	private String[] buildScreenOverlay( String url) {
	String[] insert = new String[]
	{"<ScreenOverlay id=\"Status\">",
	" <description>STEM status</description>",
	" <name>Status</name>\n",
	"<icon>",
	"<href>",
	url,
	"</href>",
	"</icon>\n",
	// following positions image to loop left
	"<overlayXY x=\"0\" y=\"1\" xunits=\"fraction\" yunits=\"fraction\"/>\n",
	"<screenXY x=\"0\" y=\"1\" xunits=\"fraction\" yunits=\"fraction\"/>\n",
	// use actual size of image
	"<size x=\"0\" y=\"0\" xunits=\"fraction\" yunits=\"fraction\"/>\n",
	"</ScreenOverlay>\n"
	};

	return insert;
	}
	/**
	* Send the KML file to the caller (GoogleEarth)
	*
	*
	* @param response
	* @param info
	* @param msg A string that will be converted
	* to an image and displayed by GoogleEarth
	* @throws IOException
	*/

	private void sendScreenOverlay(HttpServletRequest request,
	HttpServletResponse response,
	String msg)
	throws IOException {

	response.setContentType("application/keyhole");


	try {
	String host = getHost(request);
	String url = "http://"+host+"/"+
	CONTEXT+"/image?text="+
	URLEncoder.encode(msg,"UTF-8");

	String[] insert = buildScreenOverlay(url);

	PrintWriter os = new PrintWriter(response.getOutputStream());
	//PrintStream os = System.out;
	response.setContentType("application/keyhole");

	os.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
	os.println("<kml xmlns=\"http://earth.google.com/kml/2.0\">");
	os.println("<Document>");
	for (int i=0; i<insert.length; i++) {
	os.println(insert[i]);
	}
	os.println("</Document>");
	os.println("</kml>");

	os.flush();
	} catch (Exception e) {
	String emsg = "SlideShowServlet.sendScreenOverlay() failed while writing kmlFile";
	error(emsg+"\n"+e.getMessage(),null);

	}

	}


	private static String getClock() {
	long now = new Date().getTime()-start;
	return Long.toString(now);
	}

	/**
	* return the info instance associated with the specified key
	* @param key
	* @return instance of SlideShowInfo
	*/
	public static SlideShowInfo getInfo(String key) {
	SlideShowInfo info = _infoMap.get(key);
	return info;
	}
	/**
	* copy a KML file to the servlet response output stream
	* and perhaps insert additional KML statements
	*
	* @param is KML file input
	* @param os Servlet response output stream
	* @param insert optional statements to be inserted
	* after the <document> statement.
	*/
	private void copy(InputStream is, OutputStream os, String[] insert)
	throws IOException {

	InputStreamReader isr = new InputStreamReader(is);
	BufferedReader br = new BufferedReader(isr);
	String line = null;


	try {

	while (true) {
	line = br.readLine();
	if (line == null)
	break;

	byte[] buffer = line.getBytes();
	os.write(buffer, 0, buffer.length);
	if (insert!=null &&
	line.toLowerCase().startsWith("<document>")) {
	for (int i=0; i<insert.length; i++) {
	buffer = insert[i].getBytes();
	os.write(buffer, 0, buffer.length);
	}
	}
	}
	os.flush();
	os.close();
	is.close();
	} catch (Throwable e) {

	error("SlideShowServlet.copy(): Error while copying KML file. "
	+e.toString(),null);
	try {
	is.close();
	os.close();
	} catch (Exception e2) {
	// already reported it
	}
	}

	}

	/**
	* print debug messages to the server log.
	* @param msg
	*/
	public static void debug(String msg) {
	if (DEBUG) {
	Activator.logInformation(getClock()+" GEServlet: "+msg);
	}
	}

	/**
	* debug output for exceptions
	* @param msg
	* @param e
	*/
	public static void error(String msg,Throwable e) {
	//log(msg,e);
	Activator.logInformation(msg);
	if (e != null)
	if (DEBUG)
	e.printStackTrace();
	else
	Activator.logInformation(e.toString());

	}
	} // class